A typical cotton harvester includes a plurality of harvesting units supported at a forward end of a wheeled frame. Each harvesting unit includes a harvesting mechanism which picks or strips cotton from rows of cotton plants passing through a plant passage defined by each harvesting unit. Recent harvesting mechanisms include an upright picker rotor assembly including a series of vertically spaced picker spindles arranged in combination with a rotary doffer assembly. After the cotton is picked from the plants, the doffer assembly forcibly removes the cotton from the spindles and projects it rearwardly from the harvesting unit.
Some cotton harvesters presently utilize a pneumatic conveyor system which conveys cotton from the harvesting unit to a cotton receptacle typically located on the frame of the harvester. Some cotton conveyor systems typically include an upright discharge compartment which is of generally co-equal length with the height of the doffer assembly and receives the doffed cotton therefrom. The doffed cotton strikes a baffle or rear panel structure in the discharge compartment and then drops downwardly through a free fall zone to a cotton receiving suction opening at the lower end of the discharge compartment. The duct structure rearwardly extends from the suction opening and connects the discharge compartment with the cotton receptacle on the harvester. The duct structure may have one or more bends or turns along its length to compensate for the geometry of the harvester between the harvesting unit and the receptacle.
A stream of air directed into the duct structure at a location downstream of the opening creates a vacuum at the opening and induces a draft in the discharge compartment. The doffed cotton is sucked through the opening and toward an air nozzle typically used to create such a stream of air directed through the duct structure. The air stream blown from the air nozzle is sufficient to propel the cotton upstream through the duct structure and into the cotton receptacle.
Copley et al. U.S. Pat. No. 3,515,437 discloses that the entrance of air into the duct structure is in a rear wall thereof. A major problem associated with the duct design illustrated in the Copley et al. patent is the location of the air nozzle. Locating the air nozzle relatively high on the duct structure, as shown in the Copley et al. patent, significantly reduces the drawing effect within a suction area in which cotton will be initially entrained for movement toward the air nozzle. Thus, locating the air nozzle relatively high in the duct structure significantly increases the susceptibility of the duct to plugging with cotton.
Another major problem with pre-existing designs having the air nozzle inserted in a rear wall of the duct structure involves changes in direction of the air flow. As mentioned, some duct designs are configured with bends and twists along their length to compensate for the geometry of the harvester. Notably, the duct system of a cotton harvester directs not only air but also entrained cotton toward the cotton receptacle. Redirection of the air and cotton flowing past the bends and twists of the duct structure decreases the efficiency of operation.
Besides being more expensive, larger motors and compressors have failed to compensate for the losses in efficiency of operation inherent with heretofore known duct designs. Moreover, larger and therefore more expensive motors and compressors have not reduced the susceptibility of the duct system to plugging in high yield cotton harvesting conditions.